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CVE-2026-102266

9.1, critical

PyJWT is a Python implementation of JSON Web Token standards

NVD (opens in a new tab) CVE.org (opens in a new tab)
CVSS
9.1, critical critical CVSS v3.1
EPSS, next 30 days
0.2% higher than 7.2% of scored CVEs
Exploitation
Exploit code published
Published
28 Sept 202619 days ago

Description

PyJWT is a Python implementation of JSON Web Token standards. From 2.13.0 until 2.14.0, HMACAlgorithm.from_jwk is affected because PyJWK verification path used the decoded key without applying prepare_key validation. This occurs when a trusted JWK Set contains an oct entry with an empty k value. As a result, an attacker signs an HMAC token with the same zero-length key accepted by PyJWT. Consequently, forged token can carry arbitrary authenticated claims. This issue is fixed in version 2.14.0.

Details

Vendor
Jpadilla
Product
pyjwt
Weakness
CWE-347 (opens in a new tab)
Status
Analyzed
Updated
7 Oct 2026
Assigner
security-advisories@github.com

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

References 3

Exploit code 1

Patches and fixes 1

Other references 1

The kind is read from NVD's tags where present and from the shape of the URL otherwise, so treat it as a hint.

Other Jpadilla CVEs

Every Jpadilla CVE we hold

Same vendor in what we hold, not a known link between the flaws.

  • CVE-2026-102267 Jpadilla pyjwt Exposure of Sensitive Information Vulnerability EPSS 0.2% 9.1, critical
  • CVE-2026-101917 Jpadilla pyjwt Allocation of Resources Without Limits or Throttling Vulnerability EPSS 0.4% 7.5, high
  • CVE-2026-101918 PyJWT is a Python implementation of JSON Web Token standards EPSS 0.4% 7.5, high
  • CVE-2026-102274 PyJWT is a Python implementation of JSON Web Token standards EPSS 0.4% 7.5, high
  • CVE-2026-102275 PyJWT is a Python implementation of JSON Web Token standards EPSS 0.1% 8.2, high

Beyond this page

Is CVE-2026-102266 in your network?

This page tells you how dangerous CVE-2026-102266 is out there. Whether it sits on one of your devices, only a scan of your own network can tell. That is what our systems do, every day, for the companies we protect.

  • EXYS7600 OCELOT

    Find it before attackers do

    Ocelot scans your network on a schedule and reports every vulnerability it finds by its CVE identifier, with its CVSS score and how many of your hosts are affected. A finding like CVE-2026-102266 comes with the devices to patch.

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  • EXYS7950 KONDRA

    Detect it if it's exploited

    Until the patch is applied, Kondra monitors your network, events and endpoints in real time. It keeps an inventory of the software installed on every endpoint, and its anomaly detection rules flag what an attacker does once inside.

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Check your exposure

Assembled from the NVD 2.0 API, the CISA Known Exploited Vulnerabilities Catalog and FIRST EPSS. Scores are as of our last collection on 17 Oct 2026, not the live upstream state.